This invention relates to devices incorporating a rechargeable battery, such as computers and wireless phones.
U.S. Pat. No. 6,463,545, incorporated by reference in its entirety, describes a battery calibration technique. The ""545 patent describes discharging a rechargeable battery in a laptop computer to substantially zero charge in order for the computer""s charge detection circuits to accurately determine the amount of computer operating time left before the battery power runs out. While the computer is plugged into an AC outlet, a calibration circuit automatically initiates a calibration mode, whereby the main power source is decoupled from the computer, and the battery supports the computer operation until the battery discharges to a level slightly above a zero charge. This is considered a zero state, which is then used to calibrate the power management software so that the software can better determine how much battery time is left before the computer is forced to be shut down. The main power supply is then automatically reconnected to the computer, and the battery is charged normally until the battery is fully charged. After some period, not identified in the ""545 patent, the calibration technique is again commenced.
A scenario given in the ""545 patent is that the calibration technique occurs during normal computer operation when the computer is turned on and in use. However, it may be disastrous for the laptop computer operator to decide to unplug the computer from the wall during the middle of the calibration sequence and continue her work on the laptop at another location. Since the calibration sequence occurs without user intervention, the user may unplug the AC connection only to find that the battery is virtually dead due to the interruption of the calibration sequence.
One embodiment of the present invention augments the invention in the ""545 patent by only performing the automatic discharging and charging cycle during a time window authorized by the user. Such an authorized time window will most likely be a time in the middle of the night when the user does not anticipate ever using the computer unplugged from the AC outlet. Hence, if the computer is plugged into an AC outlet, the controller for the automatic discharging and charging technique reads the time of day clock in the computer, compares this clock to the authorized time window for performing the technique, and initiates the technique if the time of day falls within the authorized time window.
It is well known that a battery""s life is prolonged if it is periodically fully discharged and recharged. This relates to the memory effect of the battery. Thus, the automatic discharging and charging of the battery not only calibrates the power management system but prolongs the life of the battery while not interfering with the use of the computer.
In another embodiment, the automatic discharging and charging technique is not related to calibration, but is performed periodically to prolong the life of the battery.
In another embodiment, the authorized time window for performing the discharging and charging technique is a default time that is intended to occur at a time when the computer is typically not in use.
In another embodiment, additional techniques are used to increase the life of the battery. As mentioned above, it is known that batteries should be discharged to a low level periodically in order that they can retain a greater charge, in contrast to a battery that is constantly being topped off without first being significantly discharged. For example, when a laptop computer is plugged into the wall for long periods of time, the battery is continually or periodically being topped off. Such a battery will have a shorter useful lifetime then a battery that had been occasionally discharged by the user unplugging the computer from the wall and plugging the computer back into the wall when the xe2x80x9clow batteryxe2x80x9d alarm was signaled in the computer. To eliminate such frequent topping off, a method is carried out whereby the battery is only automatically topped off after a relatively long interval if the computer remains plugged in. Such topping off may occur after the battery charge has fallen to a certain charge level or only after an extended time period. The time period may be set by the user. Accordingly, by topping off less frequently, the battery life is extended.
The present invention is not limited to computers, but is generally applicable to all devices incorporating a rechargeable battery.